Anyone versed in the nuances of the construction industry can readily appreciate that transporting relatively large elongate objects having negligible thickness with respect to the length and width thereof favors a person who has youth and strength. Sheet rock, plywood and doors all are cumbersome to carry not only because of their size and weight, but also because one has to navigate about obstructions prevalent on a construction site.
The following patents reflect prior art techniques in overcoming these well known objections with respect to the transport of elongate articles:
______________________________________ 426,474 Smalley, et al. April 29, 1890 1,103,486 Cobb July 14, 1914 2,546,726 Creamer March 27, 1951 2,639,926 Parks May 26, 1953 3,580,601 Miles May 25, 1971 3,717,357 Schaefer February 20, 1973 3,845,969 Nadeau November 4, 1974 3,871,054 Schaefer March 18, 1975 3,942,813 Dombroski March 9, 1976 ______________________________________
Some of these prior art techniques are objectionable in that they are bulky or cumbersome themselves, others require adjustment to accomodate articles having different dimensions and some are incapable of traversing obstacles commonly found on construction sites, such as power cables, scrap lumber, etc.
For example, the patent to Cobb provides an "auto grip" form truck where the weight of the article to be carried provides a clamping force to facilitate its transport. However, should the wheels encounter an obstacle, the clamping force on the article to be carried will be directly effected by the obstacle, causing the article to temporarily become loose, causing the load to shift and/or mar the article.
Like Cobb, Nadeau provides a carrier for elongate articles which similarly encounters difficulties when confronting obstacles in the path of the wheels. To overcome this, an adjustment (48) is required to administer the clamping force and must be changed for diverse articles. Notwithstanding the adjustment, there is still a pronounced tendency to disturb the clamping force, thereby marring the article to be carried in the presence of an obstacle.
The remaining citations show the state of the art and diverge even further from the nexus of applicant's invention.